This invention relates to electrostatographic reproduction machines, and more particularly to a shield for a photoconductive member for use in an economical and capacity-extendible all-in-one process cartridge for easy adaptive use in a family of compact electrostatographic reproduction machines having different volume capacities and consumable life cycles.
Generally, the process of electrostatographic reproduction, as practiced in electrostatographic reproduction machines, includes charging a photoconductive member to a substantially uniform potential so as to sensitize the surface thereof. A charged portion of the photoconductive surface is exposed at an exposure station to a light image of an original document to be reproduced. Typically, an original document to be reproduced is placed in registration, either manually or by means of an automatic document handler, on a platen for such exposure.
Exposing an image of an original document as such at the exposure station, records an electrostatic latent image of the original image onto the photoconductive member. The recorded latent image is subsequently developed using a development apparatus by bringing a charged dry or liquid developer material into contact with the latent image. Two component and single component developer materials are commonly used. A typical two-component dry developer material has magnetic carrier granules with fusible toner particles adhering triobelectrically thereto. A single component dry developer material typically comprising toner particles only can also be used. The toner image formed by such development is subsequently transferred at a transfer station onto a copy sheet fed to such transfer station, and on which the toner particles image is then heated and permanently fused so as to form a "hardcopy" of the original image.
It is well known to provide a number of the elements and components, of an electrostatographic reproduction machine, in the form of a customer or user replaceable unit (CRU). Typically such units are each formed as a cartridge that can be inserted or removed from the machine frame by a customer or user. Reproduction machines such as copiers and printers ordinarily include consumable materials such as toner, volume limiting components such as a waste toner container, and life cycle limiting components such as a photoreceptor and a cleaning device. Because these elements of the copying machine or printer must be replaced frequently, they are more likely to be incorporated into a replaceable cartridge as above.
There are therefore various types and sizes of cartridges, varying from single machine element cartridges such as a toner cartridge, to all-in-one electrostatographic toner image forming and transfer process cartridges. The design, particularly of an all-in-one cartridge can be very costly and complicated by a need to optimize the life cycles of different elements, as well as to integrate all the included elements, while not undermining the image quality. This is particularly true for all-in-one process cartridges to be used in a family of compact electrostatographic reproduction machines having different volume capacities and elements having different life cycles.
There is therefore a need for a quality image producing, economical and capacity-extendible all-in-one process cartridge that is easily adapted for use in various machines in a family of compact electrostatographic reproduction machines having different volume capacities and elements with different life cycles.
In the xerographic process, a photoconductive surface is utilized to attract marking particles. The exposure of the photoconductive surface to prolonged periods of light significantly shorten the useful live of the photoconductive surface. The utilization of copy machines and printers with print cartridges for replacement of a combination of consumable parts including the photoconductive surface and the marking particles requires that the print cartridge be configured so as to expose at least a portion of the photoconductive surface to light so that the photoconductive surface may be in communication with the illuminating source within the printing machine.
The photoconductive surface which is exposed in the print cartridge must be protected from light and contamination during shipment and storage of spare print cartridges. Attempts have been made to protect the photoconductive surface within the printing cartridges during shipment and storage. One such prior attempts at protecting the photoconductive surface is in the form of a cover that wraps all the way around the cartridge.
These prior art wrap around covers are plagued by a series of problems. Since the photoconductive surface needs to be exposed to the illumination source within the printing machine, the cover must be removed before use of the print cartridge. The photoconductive surface is very sensitive to contamination and light and thus the cover preferably should be removed after the print cartridge is installed within the machine. Covers, however, that wrap all the way around the print cartridge are very difficult to remove from the assembly and must be removed prior to the installation of the print cartridge. Thus, the photoconductive surface is often contaminated during installation by, for example, fingers or hands contacting the photoconductive surface during installation of the print cartridge.
Further, the use of covers that wrap all the way around the cartridge often are secured by means of an adhesive, for example, in the form of a glue secured against the print cartridge cover. It becomes very difficult to remove the cover after assembly without having the glue on the cover pass by and contaminate the photoconductive surface. The presence of even a small amount of glue on the photoconductive surface will damage the photoconductive surface and result in unacceptably poor copy quality.
More recently printing cartridges have been provided with an automatic shutter mechanism that exposes the photoconductive surface as the printing cartridge is installed into the printer. Such an automatic shutter mechanism is described in U.S. Pat. No. 5,095,335. The automatic shutter mechanisms are very expensive to fabricate and assemble into the printing cartridge and are prone to mechanical problems related to repeated use. The following disclosures may be relevant to various aspects of the present invention: